Automatic slack adjuster



5 Sheets-Sheet 1 J. WILSON whi/ mi AUTOMATIC SLACK ADJUSTER June 9, 1964 Filed Sept. 10, 1962 RAJ 1720672 Z07" zfacw' Mym. i fym, 5W v 7 2/ June 9, 1964 J. WILSON AUTOMATIC SLACK ADJUSTER 5 Sheets-Sheet 2 Filed Sept. 10, 1962 YNWN June 9, 1964 J. WILSON AUTOMATIC SLACK ADJUSTER June 9, 1964 J. WILSON 3,136,393

AUTOMATIC SLACK ADJUSTER Filed Sept. 10, 1962 5 Sheets-Sheet 5 3 i5 Jae)? fils'm Q 14 M, am? .5:

' rod is located between its brake applicationflposition,

. 3,136,393 AUTQVATEC SLACK ausus'ran Jack Wilson, Chicago, Ill., assignor to Universal Railway Devices. Company, a corporation of Delaware Filed Sept. 19, 1962, Ser. No. 222,297 9 Claims. (Cl. 138-198) 1 its adjustments only after a measuring stroke that determines the direction and amount ofadjustment'required. The other commercially available, adjuster is also used in a center rod location and is of the ratchet and pawl type.

The reasons for failure or refusal of railroads to make more extensive use of the prior art two Way slack adjusters are not well defined, but it 'isknown thatdifliculties in brake shoe replacement and operation which tends to damage, fracture or break elements of the system probably had some influence. As a further objection it has been found that adjusters in-a center rod location are. overly sensitive or critical in theiroperation and control.

United States Patent O characteristics and are difficult to adapt to variations in car and brake rigging dimensions.

In view of the foregoing it is the primaryv object of the present invention to provide a two-way automatic slack adjuster for association with the cylinderdead lever of a railway braking system, and a more specific. object is to provide such an adjuster wherein the slack adjusting operations are performed primarily under the control of and in response to the position of the pushrod of the braking system. Other and related objects of the invention are to enable the automatic adjustment'of the 'un-needecladjustments, to performthe automatic take-up operations in such a way that all tendency toward slam-f rning of the elements of the braking system is prevented, tov

provide such a system wherein slack may beilet-outin substantial amounts during a brake application or while the brakes are released, to provide such an' adjuster whereinthe final applications of the brake in eachbrake application are'accomplished with the push rod terminating its movement within the allowable tolerance, to provide such an adjuster wherein objectionably sensitive or critical control characteristicsfare avoidedgand topro- ,vide such an' adjuster that may be readily and easily adapted to-normal variations in dimensions of the car and the brake rigging. I Another specific object of the "present invention is to coordinate such an automatic two-way slack adjuster with the position of the push rod'in a brake application-insuch. a way that the push rod comesto; rest in every brake application with the brake applied andfwith the push rod located substantiallyat its optimum stroke," thus to assure proper and most effective application of thebrakes in each cycleof brake operation. A j'i i i Another-object of this invention Yisi-to ;ac complish"-fau tomatic take-up operation in' such an adjuster in 'thelbraka application, but onlyafter and in 'respons'e 'solely' tdthe rnovement of the push rod into itsoptimum brake appli cation position, and an object related to the-ioregoihg is, to preventautomatictakeupat any time when thepush home position and its optimum slack to be so controlledthat there is no possibility of 1 its optimum stroke and the holding-pawl hasbeen released;

3,l36,3% Patented June 9, 1964 ice inherently limit the number of brake shoes that can be replaced at one time.

Other and further objects of the present invention will be apparent from the following description and claims, and are illustrated in the accompanyingdrawings, which, by way of illustration, show preferred embodiments of the present invention and principles thereof, and What is now' considered tobethe best mode in which to apply these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes'may be made as desired by those skilled in the art without departing from the invention.

In the drawings: FIG. 1 isa fragmentary plan 'view showing an automatic two-Way slack adjuster embodying the features of the inveritionand mounted in a conventional foundation braking system;

FIG. 1A is a fragmental portion of FIG. 1 showing the brake cylinder in its fully released position;

FIG. 2 is a side elevational view taken partially in section and showing the structure illustrated in FIG. 1; FIG. '3 is a vertical sectional view taken along the line 33 of FIG. ,1; 1 FIG. 4 is a schematic view illustrating the way in which the adjuster of this invention is associated with a braking system;

FIG. 5 is a plan sectional view of the slack adjuster unit, the view being takensubstantially'along the line 55 of FIG. 3;

FIG. 6 is a side elevational View shown in FIG. 5;

FIG. 7 is an end elevational view taken from the right in FIG. 5; i

FIG. 8 is a vertical sectional view taken substantially along the line:88 of FIG. 7;

FIG. 9 is a vertical sectional view. taken substantially I showing the parts in ,the home position of FIGS: lA,

, FIG. 12 is a view similar to FIG. ll-and illustrating the i relationship of the parts just after the workingrpawl has been freed for movement to its efiective position;

FIG; 13s a view similar to FIG." 12 and illustrating therelationship ofthe parts when the push rod has reached 14 is a view illustratingthe relationship :ofthe parts" .as the cam moves'in a reverse direction during 'a brake release operation; and,

. FIG lSQ'iasimilar diagrammaticview illustrating the relationship fofEtlidp'arts after the holding pawl has returned to'its effective relation.

I For purposes of disclosure the invention is herein illustrated'as'en bodied'in an automatic two way slack adjuster ZtLWhichisshOWn' in its operative association with of' the structure fwithin the applicable rules.

ing a push rod 22 connected to one end ofa live cylinder lever 23, and the lever 23 is connected to a dead cylinder lever 24 by a center rod 25 extended between and pivoted at its opposite ends to the levers 23 and 24 intermediate the ends thereof. One end of the dead cylinder lever 24-is operatively connected to the slack adjuster 20 as will be described, and the other ends of the levers 23 and 24 are connected by rods Zr; and 27 to the braking mechanism 26B and 27B, FIG. 4, on the trucks at opposite ends of the car. i

The slack adjuster 2t and the brake cylinder 21 are stationarily mounted on the center sill 28 of the car, while the cylinder levers 23 and 24 are movably mounted on the sill 2 8, and the end of the dead cylinder lever 24 that is associated with the adjuster 2% extends into the housing 20H of the adjuster 2t) through a slot 2 in the adjacent side of the housing and is connected bya chain 30 to a winding drum 31 located within the housing 29H. It is by rotative adjustment of the winding drum 31 that proper slack is automatically attained under the present invention so' as to assure operation of the push rod at substantially its optimum stroke in every brake application;

When the winding drum 31 is in such a rotative position as to provide the proper slack in the braking system,

operation of the push rod 22 in a brake application moves V the associated end of the live brake lever 23 to the right from the brake-released position shown in FIG. 1A toward the brake-applied position of FIGS. 1 and 2, and the resulting pivotal movement of the several associated links and levers first takes up the slack in the system and brings the brake shoes into contact with the car wheels, and in a further and relatively slight movement of the push rod 22 applies the desired braking pressure.

Braking systems of the aforesaid kind are of course designed as to relative lever lengths and the like to operate with maximum effectiveness when the push rod 22 has moved through a predetermined stroke from its fully retracted position. Under the regulations now in force in relation to railway braking systems in the United States, it is. required that the slack in the system be so adjusted that when the system is tested with the car stationary, the push rod strokeor position at full brake application be .nominally seven inches. This requirement obviously contemplates some plus or minus tolerance, and although no rule has been made defining such tolerance, .it is generally understood in the industry that plus or minus variations of about three quarters PA) of an inch are permissible, and one way automatic slack adjusters operating with such a tolerance and made under my prior Patent No. 2,562,226, patented July 31, 1951, have gone into wide use and have beenconsidered to be The. slack adjuster 20 as herein shown is particularly designed to meet such regulations and to operate Within such tolerances, and will be so described, but it should beunderstood that the disclosed structure may be varied to meet other standards thatrnay apply. a It is found that when the slack in a braking system has been set in the manner provided by the regulations above noted, the subsequent operation of the braking system with the car in motion, the vibration of the elements of the system results in an increase ofabout one inch in push rod stroke so that in practice an original at rest adjustment at a seven inch stroke results in a final push rod stroke of eight inches when the car is'in motion. 7 Because the automatic slack adjuster of thisinvention usually performs its adjusting operations while the car is in motion, the adjuster is arranged to adjust to such an increased push rod stroke, and will be so described herein. 4

Since it is the push rod position at the. time when the final braking pressure is applied that is the vital factor in attaining most efficient braking, the present invention provides for automatic control of both take-up and letout of slack by the adjuster 20 under direct control of the push rod 22 as it moves into its final position at the end of the optimum or selected push rod stroke. This is accomplished by providing a control rod 35 extending from the push rod 22 lengthwise of the car and operatively connected to the adjuster 20. The push rod 22 carries a bracket 36 through which the control rod 35 extends in a slidable relation, and a pair of nuts 37 threaded on the control rod 35 provide for coordinating the adjuster 20 with the selected or optimum push rod stroke, as will be described. At its other end the control rod 35 is pivoted to the end of a radial arm 38 that is fixed on a transverse rock shaft 40, one end of which is supported on the center sill 28 by a bearing bracket 40B, and the other end of which is supported by and operatively connected to the adjuster 2t). It is in response to the rotative position of the rock shaft 40 that the adjuster '20 is controlled to accomplish automatic take-up and let-out of slack as will be described in detail hereinafter. The adjuster 20 has an elongated generally box'like housing 20H that comprises a pair of spaced elongated are connected by a horizontal plate that is welded in position somewhat above the lower edges of plates 41 and 42. In the angle between the lower face of the plate 45 and the lower portion of the plate 41, a tubular spring housing .46 is mounted to extend from about the right hand end of the extension 44E to a point beyond the right hand ends of the plates 41 and 42, and this tubular housing is located in the angle between the plates 45 and 41in substantially a tangential relationship to these plates and is welded to such plates so that the spring housing 46 is held rigidly in position.

At about the left hand end of the horizontal plate 45, an angle bracket 47 is provided beneath the housing 20H and this angle bracket extends transversely of the housing and has one flange that projects downwardly. The upper or horizontal flange of the anglebracket 47 is engaged with the plate 42 and is welded thereto, and the .-right hand end of the angle bracket 47 engages the adjacent side of the spring housing 46 and is welded thereto so that the angle bracket 47 isheld rigidly in position. The anglebracket 47 projects to the left as shown in 'FIG. 7 somewhat beyond the plane of the housing plate .43, and this projecting portion serves as an anchoring or mounting means as will hereinafter be described.

it has been pointed out'hereinbeforc. that. the dead :cylinder lever 24 extends horizontally through an opening 29 in the housing of the slack adjuster 20, this opening 29 being in the housing plate 42 and being shown mounted at the opposite side of the center sill. .Itis in i the space between the housing plates 41 and 42 that the winding drum 31-is located, and a secondary winding dr-urn;11 -is disposed between the drum 31 and the housing plate 41with both drums fixed to and supported von a'trans verse shaft 50 that extends through all three of the plates 41, 42 and 43, and is supported therein by bearings 50B in these plates. 7

The winding drum 31 has about the drum 31in a clockwise direction and has its other end connected by means of a clevis 51 to the'e'nd of the dead lever 24 in the space between the housing one end ofthe chain 30 anchored thereon as at 30A and the chain 3t? extends The shaft 140 has the gear 63 plates 41 and 42. It will be noted that the winding drum has a groove 31G extended thereabout so that the alternate links of the chain 30 may enter the groove as the winding operation takes place.

The secondarywinding drum 131 is fixed in a rotative sense with respect to the drum 31, and a chain 139 has one end thereof anchored to the drum 131 as 'at 131A. The chain 130 is wound about the drum 131 in a direction opposite to the winding of the'chain 30 on its drum 31, the chain 130, FIG. 10, extending to the right from the lower side of the drum 131 and axially into the spring housing 46. The spring housing 46 has a fixed 130 extends. At its right hand end and-within the spring housing 46, the end of the chain is connected to a slidable cross plate 246, and an expansive coil spring 346 within the spring housing 46 surrounds the chain l'ttland acts between the fixed abutment 146 and the slidable abutment 246 to tend to impart counterclockwise rotation to the drum 131.

When the drums 31 and 131 are rotated in a counterclockwise direction as viewed in FIGS. 8 and 9, the chain 30 is tightened and slack in the braking system is reduced; or in other words, in such counterclockwise rotation of the winding drums, a take-up action is performed. Thus the spring 346 tends to impart a take-up action to the braking system, and may be termed the take-up spring.

Conversely, when the drums 31 and 131 are rotated'in a clockwise direction as viewed in FIGS. 8 and 9, the chain 30 is unwound and additional slack is introduced into the braking system. This constitutes a let-out operation, and during such a let-out operation, the take-up spring 346 is further compressed.

The rotativeinovements of the drums 31 and 131 are controlled by a ratchet and pawl structure that is located in the extension 44E of the housing H between the housing plates 42 and 43, and the effectiveness and'functioning of the ratchet and pawl structure is controlled by means that are operated by the control rodv35. Thus, a ratchet wheel 55 is mountedon the shaft 50 between the housing plates 4-2 and 43 and in a'fixed rotative relationship with respectto the two drums 31 and 131, and a holding pawl H and a working pawl W are arrangedto cooperate with the ratchet wheel 55 and these pawls H and W, .when effective, serve to prevent rotation of the ratchet wheel 55. in opposite directions; The holding pawl H is effective, when'engaged, to prevent located beneath the ratchet wheel 55' and. is mounted on a transverse shaft 56 s'oas to project upwardlyand "to theleft as viewed in FIG. 7 from such "mounted shaft.

The working pawl W is mounted to the right of the ratchet wheel 55 on a transverse'shaft57 and the workor due to variations in and extends through the plate 43 and beyond the plate 43into a small housing 143 that is rigidly fixed to the' plate 43. The housing 143 has a downwardly extending outer plate 243 as shown in FIG. 6 that is spaced from the plate 43. Within the space between the plates 43 and 243, the shaft 149 has a bifurcated arm 65 fixed thereon and the arm 65 extends downwardly and at the lower end has'a rod 66 pivoted thereto. The rod 66 extends to the right as viewed in FIGS. 2 and 6 and is 'hand end. The return'spring 68 thus tends to rock the shaft 14s in a clockwise direction to an extent that is adjustably determined by a pair of nuts 69 that are threaded onto mama 66 to the right of the bracket 47. The position that is thus determined by the adjustment of the nuts 69 serves to determine the initial or normal position of the cam 60.

The leading surfaces 160 and 260 of the cam 66 are arranged to engage and cooperate respectively with the tooth-like ends of the heads WW and 7H-of the pawls,

and the circumferential spacing of these leading surfaces 160 and 26f) is coordinated, first, with the spacing'of the pawls, and secondly, with the push rod movement or position so that under the present invention both takeup and let-out operations that are required take place'in the application phase, and in each braking cycle the cooperation of 'the pawls with the ratchet wheel assures attainment of the full braking force with the push rod 22 located within the allowable tolerance, In

attaining this result, the present invention takes into account the fact that throughout the early portions, and

' in fact, throughout a substantial portion of the push rod stroke in a brake application, the tension in the system,

and'..the positions, individual movements, and relative I movements and positions of the individual parts of the braking system tend to be erratic and to a great. extent indeterminate due to variations in slack in the system frictional resistance in different parts of the system; The pawls Hand W are formed with ratchet-engaging heads 701i and NW that are in effect self locking in that the flat end faces of the pawls engage the flat side faces of the opposed teeth and the plane of engage- .ment is in each case substantially perpendicular to the plane in which the reactive face is transmitted to the pivot pin 56 or 57'. The spacing of the pawls H and W 'about'the ratchet wheel-55 is such that when one of the pawls is in full engagement withaara'tchet tooth, the

ing pawl extends upwardly so that its upper end may 7 .move toward andaway from the ratchet wheel 55 as required. The shafts 56 and 57 extend between the housingplates 42 and "43.. Ajtension 'spring' 58 acts between the endportions .of1the twopawls H and so as to urge these pawls yieldingly-towardengaging relationship with respect to thelratchet, wheel 55.

The engagement of the pawls H and W with-theratchet transverse shaft '40 hereinbefore mentioned. I fixed on one end thereof fother pawl will have the pointed or inner end of its head disposed I'opposite the high pointer. outer end of its head disposed opposite the high point or'outer'end of a ratchet tooth. Thus, when one of the pawls. H or W hasbeen forced outwardly to, adisengaged relation, the other. one of the pawls cannot engage. fully until the ratchet wheel 55 has been shifted rotatively; so as to .allowgsuch other pawl to move into a tooth space.v Such ,rotative shifting of'the, ratchet wheel may be in either vdireetionjrbut inthe direction of movement thatis to be controlled, by a particular pawl, the shifting movement I ;'cannot gill any instance be more than one tooth space. lUn'der' the-present invention, the slack adjusterztl. is

-- constrnc'ted, arrangeda'nd controlled in 'such'a manner that'err'atic movements ofthe parts of the'braking syste'm during the early parts" of the: brake application 5 cycle and during-the brakerel'easecycle cannot'cause; false or'unnecessary'slack adjusting operations, and in accomplishing t his, the adjuster arranged so that it may' let out slack insubstantial 'amountsnot only while the braking system is fully released, as when new brake shoes are'being put in position, but also during substantially the entire time while the push rod is moving from its home position to its optimum braking position. Such an automatic let-out operation is however terminated by the working pawl W so that final braking pressure is applied with the push rod 22 in its optimum position. The attainment of this accurate termination of the push rod movement after a let-out operation results from the interrelation of the control rod movement, the tooth spacing of the ratchet wheel 55, the relationship of the pawls H and W thereto, and the relationship of the cam movements to the pawls and to the push rod position.

The automatic take-up operation under this invention is also controlled so that there can be no false or unnecessary take-up operations, and this is accomplished in such a way as to avoid slamming and breaking of the parts. Thus, the holding pawl H which governs automatic take-up is maintained effective under direct control of thepush rod 22 so that there can be no takeup operation except when the push rod 22 is at or beyond its optimum position. Hence, when there is excessive slack in the system, the push rod 22, as it advances, tightens the brake rigging gradually to the extent that is possible within the optimum stroke, and only then is the holding pawl H released. At the time when the holding pawl H is thus released, the remaining slack in the rigging is usually represented by the sum of the spacing of the several individual brake shoes from the car wheels, so that the actionof the take-up spring 346 merely completes the tightening of the rigging by completing the movement of. the several brake shoes into contact with the car wheels. All other slack has of course been taken up in the earlier portions of the push rod movement. This final taking up; of slack is accomplished quickly and with the minimum of slamming of parts, and because the initial looseness of the rigging has been taken up by the operation of the push rod, and since the push rod is then in its optimum position, the extent of the automatic take-up is limited to almost the exact amount required for establishing the proper amount of slack inv the system. The final braking pressure is therefore applied in event without exceeding the tolerance allowed as to final push rod position.

.In attaining such advantageous operation of the ad juster 20, the length of the arm 38 and the ratio of the gear 63 to the pinion 62 are selected so that movement of the control rod 35 to the right through a distance that is slightly more than one-half of the optimum push rod stroke will rotate the cam 63 clockwise from its home position of FIG.v 8, to the position shown in FIG. 13 where the holding pawl H has been fully released. With the structure herein shown this is accomplished in a four and one quarter inch right hand movement of the control rod 35. This characteristic of the adjuster is then coordinated with the push rod 22 by setting the lock nuts 37 with a predetermined spacing from the bracket 36'when both the cam 6d and the push rod 22 are in their home positions. Where the optimum push rod stroke has been selected as eight inches, thisspacing is set at three and three-fourths inches.

Thus, with this setting there is a lost motion of three and three-quarters inches between the push rod 22 and the control rod 35, and in a brake release the cam 6t) is returned to its home position of FIG. 8 when the push rod 22 has returned to its three and three-quarter inch position. Failure of the push rod 22jto fully return therefore can have no adverse influence onthe operation ofthe adjuster Zt). The employment of such a lost mo- .tion connection greatly simplifies installation. of the adjuster 2t) sincethe setting of the nuts 37' for the specified lost motion'dimension takes into account any variations in car dimensions and the like.

It has been pointed out hereinabove that as the'pawls and W are reversed between theiretfecti've and in effective: positions,.. the ratchet wheel ff ,must in every a whole.

"one direction or the other in order to engage a tooth with the pawl that has just been rendered effective, and under the present invention this characteristic is coordinated with the form of the cam era and its relationship to the pawls H and W, and with the let-out or take-up action of the ratchet wheel 55 on the braking system as Thus, it may be pointed out that the adjuster 20 and the brake cylinder 21 are in what amounts to corresponding positions in the link and lever system of the braking system, so that when the slack adjuster 2t) shifts the associated end of the dead cylinder lever 24 in one direction or the other in a predetermined amount, this has substantially the same etfect upon the stroke of the push rod 22. j i

Thus, disregarding other considerations, if the dead lever 24 has its end shifted one inch in aparticular' direction by a slack adjuster 20, a corresponding one inch variation will be produced in the required stroke of the push rod 22. This relationship is brought into effect in the present slack adjuster by relating tooth spacing of the ratchet wheel 55 to the adjusting movements of the winding drum 3t). Specifically, as applied to the present disclosure, the 24-tooth ratchet wheel 55 is so related to the effective diameter of the winding drum 31 that moveout that in a brake application the working pawl W is freed-by the cam and conditioned for engagement when the push rod 22 is approximately three-quarters of an inch away from its final or optimum'position', and

when the push rod reaches its optimum stroke, the holding pawl H is disengaged. Thus, the major portion of any letout movement that is required takes place before the working pawl W. has been conditioned for engage ment, and thereafter, the further let-out movement is limited to one tooth space because after such movement a tooth engages the working pawl W. Thus after letout adjustment, the brake application terminates with the push rod 22 substantially in its optimum position.

In the automatic take-up operation, the take-up of .the excess slack is limited by movementvof the brake shoes into contact with the wheels, andthe tape-up movement takes place when the pawl H has been shifted to its fully released position of FIG. 13. The take-upspring 346 is at this time effective to. cause. counterclockwise movement of the winding drum 31, and the action of the spring 346 is resisted by the friction in the system as well as the weight of the brake shoes and hangers- The action of .the take-up spring 346 is rapid, and yet during its operationthe entire system is under reasonable tension at all times and there can'be no excessively rapid move ment of .the lighter parts that would tend. to cause noisy operation of the breaking or breaking of. the parts.

'When all of the brake shoes have completed-their movementsinto engagementwith the associated car wheels, such take-up niovementterminates and there is an extremely rapid'build -up of tension in the brake rigging so that the ratchet wheel'55 is rocked ina' clockwise direction for a short distance which'inl every instance is less .than one toothspace. This brings the appropriate tooth of the ratchet wheel 55 into engagementwith the'working In FIGS. 11 to 15, the cam'and pawlmechanismand V 9 the related ratchet wheel 55 have been illustrated in different positions and in a diagrammatic manner as related to different rod positions that occur in the course of a brake application and subsequent brake release. In FIGS. 11 to 13, three different positions or relationships have been illustrated that take place in succession in the course of a brake application, while in FIGS. 14 and 15,

successive relationships are illustrated that take place in.

scale 76 that is graduated in inches so as to relate the rotative position of the cam 60 with the position of the push rod 22. I

It has been pointed out hereinbefore that there is an adjustment of the nuts 37 on the control rod 35' whereby provision may be made for lost motion of thepush rod 22 with respect to the control rod 35 and thecam 60. Specifically, and for illustrative purposes, the present disclosure provides for a lost motion of 3% before the brake applying movement of the push rod 22 first causes rotative. movement of the cam 60, and the'extent of this lost motion has been indicated by a suitable legend in FIG. 11 of the drawings. After the lost motion has been taken up, further advancing movement of the push rod 22 actuates the control rod and causes clockwisero push rod 22 reaches substantially the 7%" position as indicated in FIG. 12 of the drawings, the, dwell surface of the cam 60 moves beyond the end or nose of the working toward the position shown in FIG. 14. In FIG. 14 it will be noted'that the dwell surface of the cam 60 has moved to the right beyond the holding pawl H so that the holding pawl H is free for inward movement to its effective positiongbut is at this time blocked by engagement of the end of a tooth or the ratchet wheel. The leading cam surface 160 is at this time directly adjacent the head of the working pawl W. so that in further counterclockwise movement or" the cam 60, the leading surface 160 will .act to disengage I the working pawl W.

"In FIG. 15, the cam 60 is shown after it has moved further in a counterclockwise or return direction, and in the position shown in FIG. 15, the working pawl has been disengaged from the ratchet wheel 55,. With the parts in thisrelationship, the ratchet wheel 55 is free to move in approximately one tooth space in a counterclockwise .or take up direction, and'this will take place as soon as the "tension in the brake rigging is sufliciently low to be overcome by the tension in the take-up spring 346.

In the foregoing description FIGS. 11 to 15 have been described under assumed operating conditions wherein the slack in the system is present in the desired amount. 'A-ditferent operation of the mechanism takes place when 'there' is excessive slack in the system or when there is too little slack.

The ",situationlwhere there is toolittle slack in the system arises usually where one or more worn brake shoes have beenreplaced'with' a corresponding tightening' of the brake rigging. When this has been done so 'thatthere is a necessity" for'letting out slack in the next brake application, such let out of slack takes place in the application stroke of the push rod 22 and may be of relapawl Wto substantially the position shown in FIG; 12.

At this time, the working pawl W is freed so that it may move toward the ratchet wheel 55, but the relationship I When the cam 60 has reached substantially the 7 /4" position shown in FIG. 12, the leading edge 261 of the cam 60 is substantially ready to engage the holding pawl H, and as further clockwise'motion of the cam 60 proceeds, the cam surface 260 engages the pawl H and moves 'the same outwardly so as to disengage the pawl H with i respect to the teeth of the ratchet wheel55. This final disengagement of the holding pawl H takes'pla'ce when the push rod 22. has reached itsoptimum or 8" position as indicated in FIG. 13 by the relationship of the line 75 n to the scale 76. p v

Assuming that; the proper amount of slack has been established in the next preceding operation of the braking system, the ratchet wheel 55 will remain inthe same relationship'until after the working pawl. W has been freed as abovedescribed, and then as the forces in-the rigging build up, the ratchet wheel 55 'willmove for approxitively great amount so that with the present adjuster it is possible'to replace all eight brake shoes at one time.

With the slack adjuster 20 of the present invention there. may belet'out ofslack throughout the entire portion of the push rod movement from its zero position up to substantially its 7%" positionthat is indicated in FIG. 12, and the working pawl- W is at this time freed for movement inwardly to its effective position, and let out of 'Wheel is turned ina clockwise direction, and the holding pawl H rides over the teeth of the ratchet wheel 55 'insuc'cession as required by the extent of the let out movement. I When the cam and the push rod 22 have reac'hed what may be termed the 7 4"- position, the "working pawl W rides ofi. of the cam 60 into the aligned tooth space, and the final portion of the let out operation -moves the next tooth such as the tooth -T-2 intoengage men: with thelpawl W 'inthe relationship shown in FIG.

= 13. Hence, as'the-conclu'sionot a let outoperation that.

, ately one tooth space in a clockwise direction to'the' j relationship shown in FIG. l3where such movement-will be terminated by engagement of the workingpawl W with the tooth T-Z of the ratchet wheel. In the course of such clockwise movement of the ratchet wheel 55, the-push of a brake release operation, the cam 60' is'rotatedin" a].

may be of varying length asrequired, the push rod 22 =ter'minates its movement and fully applies the brakes of the [slack in the system has been established, and when the brakes; are released the parts ofthe system and of the adjuster :20 returns to; their 'nornial position's of FIG.

11 in the manner hereinbefore described, thereby to pre- 's'erveithis' adjustment. I

A -situation where there isa necessity for take-up of slack; in the; braking systemj'may arise from dilfer'ent iica s'es-. Pro ressive'wear of th b k rod 22 will'have'moved an'additional distanceof sub! g e m 6 Shoes of course stantially so thatthe push rod movement will be terini-f nated at the optimum Cir-8"v position of the push red, as indicated in FIG; 13.5 p I .3 f The reverserelationship or operation of the cam 60. and the pawls n and w is. illustrated diagrammaticallydn FIGS.14 and 15 whereit will be 'not'ed thatin thefcorirse will eventuallyrequire' take-up-in the. system, or inithe event that a brake shoe is broken and dropped out of 5 position, "atsimilar situation will :be encountered where take-upis necessary;.; Under the present inventionfsuch I I .automatic -take up takes-:place only. at;,the. end of the optimnrn-stro e of the push-rodsothat there can be no false take-lupoperations. a a 1 Thus, it will be-notedthat the holdingpawl H's-man.

tained in its effective positionat all times until the push clockwise direction. push rod 22 then starts to buildup the final tension in of the push rod.

11 rod 22 has reached its optimum or 8" position that is shown diagrammatically in FIG. 13. When the parts of the system have reached the relationship shown in FIG. 13, the'necessity for a take-up operation is as a practical matter indicated and controlled by the relationship between the force of the take-up spring 346 and opposed force provided by the tension in the brake rigging. Thus, as 'the push rod 22 has advanced from its 'zero or home position to its 8 or optimum position, a large portion of the loosenes's or slack in the brake rigging will have been taken up. For example, the chain 30, in the released position of the brakes, usually hangs in a slack position between the winding drum 31 and the dead cylinder lever 24 and this slack will be taken up early in the push rod' operation. The link and lever system will then act to move the brake hangers and brake shoes toward the wheels of the car and by the time the push rod 22 has reached its 8 or optimum position, the excess of slack in the brake rigging will be represented by the sum of the spacing of the several brake shoes from the respective wheels of the car. Otherwise the entire system or brake rigging will be under some tension, and the excess of slack in the system may then be taken up solely by completing the movement of the several brake shoes into contact with the associated wheels.

Thus when the push rod 22 reaches its optimum stroke,

, and the holding pawl H is disengaged by the leading carn surface 260, the take-up spring 346 becomes eflective toquickly com'plete the movement of the several brake shoes into engagement with-the related car wheels. As

this occurs the ratchet wheel 55 is rotated in a counter- The continued movement of the the brake rigging and when this force. exceeds the force of the take-up spring 346, the ratchet wheel 55 is actuated in a clockwise or let out direction, this clockwise or let movement is limited to less than one tooth space, at

b which time the working pawl W is engaged by a tooth of the ratchet wheel 55 'and the final braking pressure is applied at a push rod stroke of not more than 8%".

, This is within the allowable tolerance as above described.

From the foregoing description it will be apparent that the present invention provides-an automatic two-way .slack adjuster thatmay :be associated directly with the cylinder dead lever of a railway braking system, and which is controlled in its action directly by the position It will also be evident that with the adjuster of this invention each brake application is accomplished within the allowable tolerance as to push rod stroke, thus to assure efficient brake application, and under the present invention the adjuster may be readily applied to railway cars to attain proper-automatic slack adjustment despite variations in car dimensions and the like.

It will also be evident that under the present invention,

the automatic take up of slack is controlledin a, novel manner so as to prevent excessive or unneeded take .up.

q Furtheritwill be apparent that the present invention provides an automatic two wayslack adjuster in which :critical; control *characteristics are avoided and which simplifies replacementof brakeshoes inthe breaking .system.

Thus, while preferred embodiments of the invention have been illustrated herein, it is to be understood that. -;changes and variations maybe made by. those skilled; in.,the art withoutzdepa'rting fromrthe spirit" andqscope 1 the aPPending'claims. 1 v U l .I claimz t *1. An automatic adjusting the cylinder deadlever ofarailway foundation; 5 braking s'ystem that is designed 'to eflect brake application with the push rodlocated within a predetermined plus or minus tolerance of apredetermined optimum push rod stroke; said adjuster comprising a housing having a toothed two-way slack adjuster adapted 'for ratchet wheel and a pair of winding drums mounted for 'rotation in unison on a predetermined axis for opposite rotative movement in let out and take-up directions, a flexible member anchored at one end on one of said drums in position to be wound thereon in let out movement, takup spring means acting on said flexible member to urge said winding drumsin a take-up direction, a chain adapted "to be connected at one end to such a dead lever and con nected at its other end to the other winding drum in posi tion to be wound thereon in a take-up movement of such drum, a holding pawl mounted on said support member and operable when effective to engage a tooth of the ratchet wheel to prevent such take-up movement, a work ing pawl mounted on said support and operable when eflective to engage a tooth of said ratchet wheelto prevent such let out movement, said ratchet wheel having a tooth spacing equivalent in the system to a push rod movement that does not exceed said tolerance dimension, said pawls being spaced so that when one pawl is fully engaged with a tooth theotherpawl is locatedopposite the top of another tooth, cam means rotatable on said axis adjacent said toothed member and having cam surfaces operable to free one pawl for engagement and then to promptly disengage the other pawl, and means adapted for operative connection with the push rod of such a system for operating said cam in a brake application to free said working pawl for engagement when the'push rod reaches the lower tolerance limit, for disengaging said holding pawl when the push rod reaches its optimum position for freeing said holding pawl forengagement in a brake release when the push rod reaches said optimum position; and for then promptly disengaging said working pawl.

2.fAn automatic two-way slack adjuster adapted for I adjusting the anchor point of the'cylinder dead lever of a railway foundation brake system that is designed toefliect brakeapplication with the push rod located withina predetermined plus or minus tolerance of a predetermined optimum push rod stroke; said adjuster comprising a housing having a toothed ratchet wheel, a take-up drum and ,an adjusting drum mounted in the housing for rotation in unison on a predetermined axis for opposite rotative movement in' let out and take-up directions, a flexible member anchored at one end on one of said drums in position to be wound thereon in let out movement, take-up spring means-acting on said flexible member to urge said winding drums in a take-up'direction, a chain adapted to be connected at one end'to such a dead lever and connected to its other end to the other winding drum'in position to be wound thereon in a take-up movement of such drum, a holding pawland a working pawl mounted on said support member and operable, when effective, to engage a tooth of the ratchet wheelto prevent such take-up ,and let outmo'vements, respectively, said ratchetwheel having a tooth spacing equivalent in the system to a push rod movement through said tolerance" dimension, said pawls being spaced so that when one pawl is fully'engaged with a tooththe other pawl is located opposite the top of U another tooth, cam meansrotatable on said axis adjacent said toothed member and having cam surfaces operable to free one'pawl for engagement and then to promptly disengage'the other pawl, spring return means for urging -'said cam to a predetermined home position, and means adapted for operative connection with the push rod of such asystem for operating said camin abrake application" to free said working'pawl for engagement when the push rod reaches the lower tolerancelimit and for disengaging 7 said holding pawl when the push rodj reaches its optimum position.

and is designed. to effect brakei application with a power operated push rodloc ated within a predetermined plus or I lminus toler'ance of a predetermined optimum push rod 13 stroke; said adjustor comprising a support member stationarily mounted with respect to the operating elements and a ratchet member connected together in a guided relation for opposing relative movement in let-out and takeup directions in increments that do not exceed said tolerance, and said ratchet member having teeth thereon, said teeth having a spacing equal to said increments, take-up spring means acting to urge said members relative to each other in a slack take-up direction, a holding pawl and a working pawl pivotally mounted on axes which are fixed relative to said support member and said pawls urged yieldingly toward said teeth wherein said holding pawl prevents take-up movement and said working pawl prevents let-out movement of said ratchet member when engaged with said teeth, said pawls being positioned so that when one pawl is fully engaged with said teeth the other pawl is located opposite the end of one of said teeth, cam means movably mounted relative to said support member so as to be movable along the ratchet member in brake engagement and brake release directions for controlling engagement of said pawls with said teeth and operable in accordance with its direction of movement during brake application to first free the working pawl for engagement with said teeth and then after further movement of the cam means through a distance substantially equal to one such tooth space to disengage the holding pawl from said teeth, cam return means operable to yieldingly urge said cam means in a return direction to a position wherein said holding pawl is engaged and said working pawl is disengaged from said teeth, said cam means having a leading surface adapted to be moved in a brake engaging direction for disengaging said holding pawl, said leading surface being spaced from said holding pawl when said brake system is in a brake releasing position so that disengagement of said holding pawl may be eflected only by movement of the cam means in a brake engaging direction through a distance substantially greater than one tooth space, a cam operator separate from said operating elements connected to said cam means, lost motion means connected to said cam operator and adapted for connecting it to said push rod, said cam operator actuating said cam means to disengage said holding pawl when the push rod reaches its optimum stroke during brake application.

4. A slack adjuster as defined in claim 3, wherein said teeth each have a pair of side surfaces converging to a fiat end surface.

5. A slack adjustor as defined in claim 3, wherein said cam means includes a trailing surface and a smooth surface extending between said leading and trailing surfaces, said smooth surface adapted to successively prevent engagement between each of said pawls and said teeth.

6. In a railway foundation braking system that is designed to effect brake application with the push rod located within a predetermined tolerance of a predetermined optimum push rod stroke, the combination of a stationarily mounted housing into which one end of the dead cylinder lever extends, a toothed ratchet wheel and first and second winding drums supported on a common axis in said housing for rotation in unison, spring means and a take-up chain connected to said first drum to yieldingly urge said drums and ratchet wheel rotatively in a take-up direction, a load chain connected between the second drum and said end of the dead cylinder lever for adjustably determining the working position of the lever, oppositely acting let-out control and take-up control pawls pivoted in said housing for engaging the ratchet member, a control cam rotatable on said axis for rendering said pawls eifective alternately by freeing one pawl for engagement and then disengaging the other pawl, resilient cam return means normally holding said cam in a home position wherein said take-up control pawl is engaged with said ratchet, and control means connected to the push rod and operating said cam against the action of said cam return means to reverse said pawls and complete the disengagement of said take-up pawl at the time when said push rod reaches its optimum stroke in a brake application.

7. A braking system according to claim 6 wherein said control cam acts on the let-out control pawl to free the letout control pawl for engagement only when the push rod has moved beyond the lower tolerance position and wherein the control cam cooperates with the take-up control pawl to free the take-up control pawl for engagement whenever the push rod is between said optimum position and its home position.

8. A braking system according to claim 6 wherein said control cam acts on the let-out control pawl to free the let-out control pawl for engagement only when the push rod has moved beyond the lower tolerance position.

9. A braking system according to claim 6 wherein said control means is in the form of an elongated pull rod having a lost motion connection with the push rod so that the cam is actuated only after the push rod has moved for a predetermined distance from its home position.

References Cited in the file of this patent UNITED STATES PATENTS 2,620,902 Wilson Dec. 9, 1952 3,001,612 Mersereau Sept. 26, 1961 3,025,932 Broling Mar. 20, 1962 

1. AN AUTOMATIC TWO-WAY SLACK ADJUSTOR ADAPTED FOR ADJUSTING THE CYLINDER DEAD LEVER OF A RAILWAY FOUNDATION BRAKING SYSTEM THAT IS DESIGNED TO EFFECT BRAKE APPLICATION WITH THE PUSH ROD LOCATED WITHIN A PREDETERMINED PLUS OR MINUS TOLERANCE OF A PREDETERMINED OPTIMUM PUSH ROD STROKE; SAID ADJUSTER COMPRISING A HOUSING HAVING A TOOTHED RATCHET WHEEL AND A PAIR OF WINDING DRUMS MOUNTED FOR ROTATION IN UNISON ON A PREDETERMINED AXIS FOR OPPOSITE ROTATIVE MOVEMENT IN LET OUT AND TAKE-UP DIRECTIONS, A FLEXIBLE MEMBER ANCHORED AT ONE END ON ONE OF SAID DRUMS IN POSITION TO BE WOUND THEREON IN LET OUT MOVEMENT, TAKUP SPRING MEANS ACTING ON SAID FLEXIBLE MEMBER TO URGE SAID WINDING DRUMS IN A TAKE-UP DIRECTION, A CHAIN ADAPTED TO BE CONNECTED AT ONE END TO SUCH A DEAD LEVER AND CONNECTED AT ITS OTHER END TO THE OTHER WINDING DRUM IN POSITION TO BE WOUND THEREON IN A TAKE-UP MOVEMENT OF SUCH DRUM, A HOLDING PAWL MOUNTED ON SAID SUPPORT MEMBER AND OPERABLE WHEN EFFECTIVE TO ENGAGE A TOOTH OF THE RATCHET WHEEL TO PREVENT SUCH TAKE-UP MOVEMENT, A WORKING PAWL MOUNTED ON SAID SUPPORT AND OPERABLE WHEN EFFEC- 